全文获取类型
收费全文 | 12091篇 |
免费 | 607篇 |
国内免费 | 257篇 |
专业分类
耳鼻咽喉 | 85篇 |
儿科学 | 236篇 |
妇产科学 | 269篇 |
基础医学 | 2049篇 |
口腔科学 | 104篇 |
临床医学 | 1063篇 |
内科学 | 1655篇 |
皮肤病学 | 35篇 |
神经病学 | 1334篇 |
特种医学 | 256篇 |
外国民族医学 | 1篇 |
外科学 | 1729篇 |
综合类 | 939篇 |
一般理论 | 1篇 |
预防医学 | 485篇 |
眼科学 | 145篇 |
药学 | 1667篇 |
3篇 | |
中国医学 | 236篇 |
肿瘤学 | 663篇 |
出版年
2024年 | 20篇 |
2023年 | 130篇 |
2022年 | 278篇 |
2021年 | 412篇 |
2020年 | 274篇 |
2019年 | 255篇 |
2018年 | 266篇 |
2017年 | 286篇 |
2016年 | 302篇 |
2015年 | 334篇 |
2014年 | 500篇 |
2013年 | 811篇 |
2012年 | 462篇 |
2011年 | 488篇 |
2010年 | 397篇 |
2009年 | 490篇 |
2008年 | 496篇 |
2007年 | 486篇 |
2006年 | 421篇 |
2005年 | 438篇 |
2004年 | 349篇 |
2003年 | 335篇 |
2002年 | 274篇 |
2001年 | 274篇 |
2000年 | 213篇 |
1999年 | 244篇 |
1998年 | 240篇 |
1997年 | 223篇 |
1996年 | 222篇 |
1995年 | 234篇 |
1994年 | 203篇 |
1993年 | 176篇 |
1992年 | 163篇 |
1991年 | 162篇 |
1990年 | 145篇 |
1989年 | 152篇 |
1988年 | 137篇 |
1987年 | 158篇 |
1986年 | 160篇 |
1985年 | 214篇 |
1984年 | 186篇 |
1983年 | 133篇 |
1982年 | 163篇 |
1981年 | 150篇 |
1980年 | 147篇 |
1979年 | 93篇 |
1978年 | 79篇 |
1977年 | 60篇 |
1976年 | 47篇 |
1975年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
目的 研究大鼠前庭神经核群向脊髓的投射纤维特征。方法 在 7例SD大鼠采用结合生物素的葡聚糖胺(BDA)逆行法观察大鼠前庭核群向脊髓的投射。结果 除前庭神经上核 (SVN)外的其余各前庭核均有向大鼠腰髓的投射 ,单侧注射的实验动物中 ,前庭神经内侧核 (MVN)、外侧核 (LVN)和降核 (DVN)的标记神经元可见于双侧 ,其中MVN和LVN的标记神经元以注射同侧占优势 ,而DVN标记神经元两侧数量基本一致。结论 大鼠前庭脊髓尾侧束发出纤维投向脊髓腰段 相似文献
62.
Many eukaryotic cells depend on proper cell polarization for their development and physiological function. The establishment of these polarities often involve the subcellular localization of a specific subset of proteins, RNAs and organelles. In Drosophila, the microtubule-dependent BicD (BicaudalD) localization machinery is involved in the proper localization of mRNA during oogenesis and embryogenesis and the proper positioning of the oocyte and photoreceptor nuclei. BicD acts together with the minus-end directed motor dynein as well as Egl and Lis-1. The finding that the mammalian homologs of BicD function in retrograde Golgi-to-ER transport has supported the view that BicD may be part of a repeatedly used and evolutionary conserved localization machinery. In this review we focus on the various processes in which BicD is involved during Drosophilian development and in mammals. In addition, we evaluate the interactions between BicD, the dynein localization machinery and associated factors. 相似文献
63.
Kiyosumi Shibata Fumitaka Kikkawa Akihiko Nawa Koji Tamakoshi Nobuhiko Suganuma Yutaka Tomoda 《Clinical & experimental metastasis》1997,15(6):612-619
Ovarian cancer cells disseminate by attachment to the peritoneal mesothelial cell surface of the abdominal cavity. We therefore investigated the influence of conditioned medium (CM) from human peritoneal tissues and mesothelial cells on the secretion of matrix metalloproteinases (MMPs) by ovarian cancer cells. The molecular weights of MMPs stimulating factors derived from human peritoneal tissues and mesothelial cells were estimated using microconcentrators with various cut-off membranes. Human peritoneal tissues were obtained from 12 surgical patients, and mesothelial cells were isolated from three peritoneal specimens. Exposure to CM from peritoneal tissue caused a concentration-dependent increase of the MMP-2 and MMP-9 bands in CM from NOM1 ovarian cancer cells, as shown by zymography. There was a significant difference in the increase of MMP-2 and MMP-9 (2.46-fold and 7.14-fold, respectively, at 0.4mg/ml protein; P < 0.005). CM from mesothelial cells also significantly increased the secretion of MMP-9 by NOM1 cells. The molecular size of possible MMP-9-stimulating factors secreted by peritoneal tissues and mesothelial cells was above M 100000. Further, CM of peritoneal tissues and mesothelial cells also induced the invasiveness of NOM1 cells. These findings suggest that mesothelial cells may secrete some factors which predominantly induce the MMP-9 production and increase invading cell numbers. 相似文献
64.
Yoshinori Umesaki Takaji Yajima Kiyoshi Tohyama Masahiko Mutai 《Pflügers Archiv : European journal of physiology》1980,388(3):205-209
The characteristics of acetate uptake by colonic epithelial cells of the rat were studied. Clear saturation kinetics of acetate uptake were not observed in these experiments at either 0° C or 30° C. A decrease in the pH of the medium markedly increased the acetate uptake. The activation energy for acetete uptake derived from an Arrhenius plot was about 6.1 kcal/mole. Among the inhibitors tested, no effective inhibition of acetate uptake at 0° C was observer. Metabolic inhibitors severely inhibited transport at 30° C. Inhibition of acetate uptake by other short chain fatty acids, which was non-competitive, was observed. The finding that efflux from the cells was stimulated in the presence of compounds such as pyruvate and bicarbonate supported the notion of a close interrelationship between weak electrolyte transports in vivo. Although the H+ gradient across the cell membrane is suggested to be one of the factors determining the uptake rate, it seems difficult to explain all the results in this way. 相似文献
65.
V. V. Teplova V. P. Zinchenko Yu. V. Evtodienko 《Bulletin of experimental biology and medicine》1977,84(2):1159-1162
The pattern of Ca2+ accumulation by tumor mitochondria (MC) was investigated under various experimental conditions. In the absence of penetrating anions tumor MC were shown to take up Ca2+ in only one fifth the amount taken up by liver MC. In the presence of acetate this difference was greater still. Inorganic phosphate (Pin) abolished the observed defects of Ca2+ transport and increased the Ca2+ capacity of the tumor MC considerably. By contrast with liver MC, Pin also had a stabilizing effect on membrane permeability of the tumor MC; this may be the cause of the increasee Ca2+ capacity of these MC.Department of Bioenergetics, Institute of Biological Physics, Academy of Sciences of the USSR, Pushchino-on-Oka. (Presented by Academician of the Academy of Medical Sciences of the USSR S. E. Severin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 84, No. 8, pp. 202–205, August, 1977. 相似文献
66.
For highly diffusive solutes the kinetics of blood–tissue exchange is only poorly represented by a model consisting of sets of independent parallel capillary–tissue units. We constructed a more realistic multicapillary network model conforming statistically to morphometric data. Flows through the tortuous paths in the network were calculated based on constant resistance per unit length throughout the network and the resulting advective intracapillary velocity field was used as a framework for describing the extravascular diffusion of a substance for which there is no barrier or permeability limitation. Simulated impulse responses from the system, analogous to tracer water outflow dilution curves, showed flow-limited behavior over a range of flows from about 2 to 5 ml min–1 g–1, as is observed for water in the heart in vivo. The present model serves as a reference standard against which to evaluate computationally simpler, less physically realistic models. The simulated outflow curves from the network model, like experimental water curves, were matched to outflow curves from the commonly used axially distributed models only by setting the capillary wall permeability–surface area (PS) to a value so artifactually low that it is incompatible with the experimental observations that transport is flow limited. However, simple axially distributed models with appropriately high PSs will fit water outflow dilution curves if axial diffusion coefficients are set at high enough values to account for enhanced dispersion due to the complex geometry of the capillary network. Without incorporating this enhanced dispersion, when applied to experimental curves over a range of flows, the simpler models give a false inference that there is recruitment of capillary surface area with increasing flow. Thus distributed models must account for diffusional as well as permeation processes to provide physiologically appropriate parameter estimates. © 2000 Biomedical Engineering Society.
PAC00: 8719-j, 8710+e 相似文献
67.
Summary The present communication endeavours to elucidate the mechanism of histamine release from rat peritoneal mast cells induced by selective histamine liberators.Of the different enzymatic processes involved in secretion the following are considered: ecto-ATPase activity in the mast cell, pro-esterase-esterase conversion during histamine secretion, cyclic AMP and microtubule association/dissociation, phospholipase A2 and the effect of phospholipid metabolites on secretion, N-methyl transferase and the methylation of phospholipids and the phosphorylation and desphosphorylation of proteins. 相似文献
68.
Mid-log phase Leishmania donovani promastigotes accumulated 2-deoxy-d-glucose (2-DOG) via a carrier mediated transport system, maintaining an apparent Km of 24.4 μM and a Vmax of 3.12 nmol mg?1 protein min?1. d-Glucose but not l-glucose competitively inhibited the 2-DOG transport with an apparent Ki of 18.7 μM. Transport of 2-DOG was inhibited by 2,4-dinitrophenol and NaN3. The parasites maintained a 2-DOG gradient of at least 79 fold across the surface membrane, demonstrating the active nature of the transport system. 相似文献
69.
J. L. Borke A. Caride A. K. Verma J. T. Penniston R. Kumar 《Pflügers Archiv : European journal of physiology》1990,417(1):120-122
We used a monoclonal antibody (5F10) specific for the human erythrocyte plasma membrane Ca++-pump to demonstrate the presence and distribution of Ca++-pump epitopes in rat intestine. In paraffin embedded tissue sections, antibody 5F10 binds to epitopes in the basolateral membranes of absorptive cells in rat duodenum and portions of jejunum but not ileum. Western blot analysis of intestinal mucosal proteins with antibody 5F10 shows binding of antibody to major bands of Mr 135,000 and Mr 72,000, and to lesser bands of Mr 125,000 and Mr 27,000. This pattern was seen in mucosal homogenates of rat duodenal and jejunal cells and to a lesser extent in ileal cells. The Mr 135,000 band corresponds to the molecular weight of Ca++-pumps in other tissues. The other bands correspond in size to known proteolytic fragments of the Ca++-pump. Slot-blot analysis of nitrocellulose immobilized mucosal homogenates shows binding of 5F10 to be greatest in duodenum and least in ileum. Ca++- transport studies by the everted gut sac technique show a correlation between vitamin D induction of active Ca++-transport and the segmental distribution of Ca++-pump epitopes. 相似文献
70.
Larsen MV Lundegaard C Lamberth K Buus S Brunak S Lund O Nielsen M 《European journal of immunology》2005,35(8):2295-2303
Reverse immunogenetic approaches attempt to optimize the selection of candidate epitopes, and thus minimize the experimental effort needed to identify new epitopes. When predicting cytotoxic T cell epitopes, the main focus has been on the highly specific MHC class I binding event. Methods have also been developed for predicting the antigen-processing steps preceding MHC class I binding, including proteasomal cleavage and transporter associated with antigen processing (TAP) transport efficiency. Here, we use a dataset obtained from the SYFPEITHI database to show that a method integrating predictions of MHC class I binding affinity, TAP transport efficiency, and C-terminal proteasomal cleavage outperforms any of the individual methods. Using an independent evaluation dataset of HIV epitopes from the Los Alamos database, the validity of the integrated method is confirmed. The performance of the integrated method is found to be significantly higher than that of the two publicly available prediction methods BIMAS and SYFPEITHI. To identify 85% of the epitopes in the HIV dataset, 9% and 10% of all possible nonamers in the HIV proteins must be tested when using the BIMAS and SYFPEITHI methods, respectively, for the selection of candidate epitopes. This number is reduced to 7% when using the integrated method. In practical terms, this means that the experimental effort needed to identify an epitope in a hypothetical protein with 85% probability is reduced by 20-30% when using the integrated method.The method is available at http://www.cbs.dtu.dk/services/NetCTL. Supplementary material is available at http://www.cbs.dtu.dk/suppl/immunology/CTL.php. 相似文献